What bomb for will of the emperor?

Hey, I have seen some people use NT and other use FrostBomb, what exact is the difference? I am guessing NT if you are double dotting bosses all the time, and FrostBomb you use to explode on the adds? Which would you guys would be better? (10m - playing frost..)

They are virtually identical; FB does more damage in AOE and provides a more predictable rotaion, NT does more single target damage but you have to cross your fingers for procs. The difference in DPS is in the hundreds and thus not really statistically significant.
You may want to use NT eventually though because the Elegon trinket procs from DoT ticks and does not count Frost Bomb.

Depends on how many other casters you have as loot competition really.

nether tempest probably. no limit on target (not saying im going to put it more than 2)

but it will be better for dotting up both bosses and i dont think we will have slowing issue (besides frost bomb stinks for arcane :P)

then again spamming nether tempest aint the best of ideas out there either

But ye generally speaking it doesnt make much difference which bomb you choose, though if you can max frost bomb on will of the emperor as a frost mage properly it has benefits like slowing the adds and doing massive shatter damage.

Some good advice here already. My opinion is to go with Frost Bomb just to help mop up the smaller adds. They can be a pain so you want to take them out as quickly and efficiently as possible (and NT is not overly efficient once you are putting it on multiple targets). Also the frost shatter you get from the Bomb can provide a nice boost and help control the adds as well.